Pseudo Toy SQLite clone in php

usosql.php

?php

define("EXIT_SUCCESS", 0);
define("EXIT_FAILURE", 1);

class InputBuffer
{
	public ?string $buffer;
	public int	   $buffer_length;
	public int	   $input_length;

	public function __construct() {
		$this->buffer = null;
		$this->buffer_length = 0;
		$this->input_length = 0;
	}	
}

function print_prompt(): void {
	echo "db > ";
}

function read_input(InputBuffer $input_buffer): void {
	$input = fgets(STDIN);
	$input_buffer->buffer_length = strlen($input);

	if ($input === false) {
		echo "Error reading input", PHP_EOL;
		exit(EXIT_FAILURE);
	}

	$input_buffer->buffer = trim($input);
	$input_buffer->input_length= strlen($input_buffer->buffer);
}

function close_input_buffer(InputBuffer $input_buffer): void {
	$input_buffer = null;
}	

/**
 * main
 */
$input_buffer = new InputBuffer();

while (true) {
	print_prompt();
	read_input($input_buffer);

	if ($input_buffer->buffer === ".exit") {
		close_input_buffer($input_buffer);
		exit(EXIT_SUCCESS);
	} else {
		echo "Unrecognized command ", $input_buffer->buffer, PHP_EOL;
	}
}